Attn Jon - serial object...

FORD

Hi Jon,
I have been messing with the serial lcd object you kindly shared. Our LCD is Seetron BPP-420.
This is fixed at N81, 2400 or 9600. Should the object work OK with that do you know ?

I have checked and we are getting·5v, 0v and clean serial data to the display (have tried a couple of displays).
But we have no display, so I was wondering if the code you gave is inverted or true ?

Cheers,
Chris

Jon Williams

Chris,

The BPP-420 has two modes: normal and "old" (for BPI-216 compatibility).· If you want to use the newer features of the LCD (normal mode), use the program I've attached.· I·created a custom BPP-420 object (using normal mode features) and translated the SEETRON demo.· I'll probably update the BPI-216 object for BPP-420 compatibility.

The great news is that it worked the first time!· This stuff (Propeller programming)·is starting to sink in.

Update:·I found a "gotcha" in one of the [noparse][[/noparse]infrequently used] methods -- fixed it.· And I found a BPP-440 in the parts drawer, so I made an object·for it too.

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Jon Williams
Applications Engineer, Parallax

Post Edited (Jon Williams (Parallax)) : 4/19/2006 4:51:01 PM GMT

Stan671

Thanks for both the BPP-420 and 216 demo programs.· Since all of my projects·have a serial LCD on them and I use them for most of my debugging, this is the first routine I will need to get working.

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Stan Dobrowski

FORD

A major thanks Jon,

Will let you know how it goes later.

Chris

Jon Williams

You're welcome, Chris.· I decided not to manipulate the BPI-216 object, instead, I made a BPK-000 object.· I've tested the code with the BPI-216 and BPP-420 (in "old" mode) and it works fine.

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Jon Williams
Applications Engineer, Parallax

FORD

Hello Jon,
I must have a hardware issue.
Are you driving the display directly from an i/o with no pullup / down ?

Chris

Jon Williams

Straight out of the chip -- as you can see in the picture.· Now, I have noticed that I get occasional noise issues at 9600 baud, I think this is to do with my loose wires and noise from the environment; I never see this at 2400 baud (or with the Parallax display that uses an SX chip at 9600).

BTW, if you look at the SEETRON docs you'll see that Scott uses a divider (22k series / 220k to ground) that holds the line low and allows the modules to be used with RS-232 levels (see below).· This is knocking the 3.3v Propeller output down a bit, so in an industrial application I would suggest you put a non-inverting buffer (with a 5v output)·between the Propeller and the SEETRON display.

Sin >---[noparse][[/noparse] 22k ]---+---- to PIC
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Jon Williams
Applications Engineer, Parallax

FORD

Jon,
I am driving it straight out of the chip, and it all looks clean on a scope, full swing 0 - 3.3v, measured at the LCD end of the wiring.
I have tried it at 2400 and 9600.
If I 'scratch' the 5v and signal lines together very briefly, I get junk on the display (as expected), so I think it is definately a signal level thing.
Have tried different i/o's as well, no different.

I gotta do some real work for a while, so will get back onto it later.

I think I might just try a transistor to boost the voltage to the display and see how that goes, otherwise, I'll do the buffer thing.

Thanks Jon, and sorry for the stuffing around.

FORD

Hello Jon,
Got it all going. Now that I can see whats happening, I can get a better understanding. Next, serial keypad input.

The solution was as you suggested. I simply used a 4050 non-inverting buffer to boost the 3.3v to a 5v signal for the Seetron display.

Thanks again for your help / time with this.

Cheers,
Chris

Jon Williams

No worries, Chris, but you owe me a beer if I ever make it back "down under."

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Jon Williams
Applications Engineer, Parallax

FORD

Absolutely always got a 'coldy' in the fridge, could even arrange for a few Budweisers to be in there if you were heading this way.

Otherwise, If I ever get to the US, I'll knock on your door with my head.. because my arms will be full of beer.

Cheers,

Chris